Concentration of barite



Patented Mar. 13, 1928.

UNITED STATES PATENT oFFicE.

WALTER O, BORCHERDT, OF AUSTINVILLE, VIRGINIA, ASSIGNOR TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

CONCENTRATIQN F BARITE.

Ho Drawing.

This invention relates to the concentration of barite from barite ores or other baritebearing material, and has for its object the provision of an improved process of concentrating barite b selective froth-flotation.

Barium sulfate BaSO occurs in nature.

in varying degrees of purity and I goes by the names barite, barytes and heavy spar.-

It is important to note for the purpose of 'the present invention, the distinction between -the use of the term floated as at present employed in the trade with reference to barytes such as the National Pigments and Chemical Company brand Foam A, the imported brands S. W. 000. or Eagle and the use of the term floated as employed herein to designate the product of the present invention. As at resent used in the trade, the term floated indicates only that the barite has been finely ground and momentarily suspended in water, that is, that the barite has been subjected to an ordinary hydraulic classification treatment, such as is used in the preparationof many other finely divided materials, the method of procedure and choice of apparatus for which are well known to those skilled in the art of gravity concentration of minerals. Emphasls is placed upon this point in order to obvlate the possible misa prehension that floated" barytesas hereto ore used by the trade re fers to the product of a froth-flotation of barite-bearing material. So far as I am aware, I am the first to produce by the method of froth-flotation a high grade barite concentrate with a high recovery of the barite value from an ordinary crude barite ore containing im urities which would render it unavailable or use in the manufacture of prime white grade barytes or western domestic floated barytes, or from waste or middlings products from the ordinary gravity concentration of barite ores which would also be unavailable for the commercial production by current methods of Western domestic floated barytes. v Barite is rather unique amon the minerals in that for most of its applications an extremely high degree of purity pf the concentrat'e'is required. Lump barite 1s ordi- Application filed August 27, 1924. Serial No. 734,545.

sired. There are both technical and economic reasons for this situation. Some of the common impurities of barite act not only as diluents, causing a degradation of the material, but also have a positive deleterious action because of their'influence in the further processes of treatment to which the material is subjected or upon the final product in which the barite is used. Manganese cannot be eliminated by ordinary acid bleaching nor can iron, when present in excess of-one per cent. Unless the impurities can be very easily and completely removed, the technical objection to their presence taken in connection with the relatively high cost of removing them from a material whose final market value is comparatively low, imposes a limitation which with many barite deposits has so far not been successfully overcome. Thatis to say, there are many known deposits of barite in which a considerable tonnage of barium sulfate exists, but either because the grade is low or the impurities are especially objectionable, these deposits have so far been unavailable for commercial exploitation.

Barite is a relatively soft and friable mineral, and in grinding therefore tends to grind finer under given conditions than many of the minerals with which it is associated. Since in ordinary gravity concentration of minerals, sliming is to be specially avoided because of the difiiculty of handling the extremely fine-size mineral particles in gravity concentrating machines, this characteristic of the mineral operates commercially to inhibit concentration below a certain range of particle size. It, therefore has been and is now customary to discar certain products during the concentration of barite ore, despite the fact that they contain a considerable quantity of barite, since heretofore the cost of recovering this barite has outweighed the possible profit from the 100 operation; in part for the reason before stated, and in part because the impurities with which the barite is associated often have a specific gravity so close to that of the barite itself as to render gravity concen- 5 tration difiicult and uneconomical.

Because of these limitations, imposed by the necessity for great purity in the concentrate, the severe sliming of the mineral upon fine grinding, the comparatively narrow range of difference in specific gravity between barite and its most serious impurities, and the economic limitation resulting from the narrow margin of profit; not only have many deposits of barite proved unavailable for present use and many by-products been thrown to waste or stored for possible future utilization, but there has been much less elaboration of gravity concentration plants for the treatment of barite than has been the case with the gravity concentration plants treating ores of lead, zins, copper and other valuable minerals.

The present invention contemplates the concentration of barite by froth-floation. In carrying out the invention the barite-bearing material is subjected to froth-flotation in the pretence of a barite-selective flotation agent, thereby effecting a substantial concentration of the barite in the resulting overflow froth. More particularly, the invention contemplates the provision of a method of concentrating barite by froth-flotation in which high recovery of barite is effected and at the same time a high grade barite concentrate is produced. Thus, the present invention contemplates, with respect to this aspect thereof, an ultimate recovery of at least 60% of the barite in an overflow froth containing not leJs than 90% barite.

As the result of a long series of careful tests using a number of barite ores and the flotation agents which are most commonly successful in the flotation of sulfids, I have found that with a few exceptions such sulfid flotation agents are either wholly ineffectual for the forth-flotation of barite on a basis which will yield high grade commercial concentrates and high recovery, or that they produce flotation of only the most finely divided barite, with very low recoveries of the barite contained in the ore. The exceptions noted in the preceding sentence are flotation agents which are generally of inferior value for the flotation of sulfids because of their marked gangue-lifting tendency, and they are in fact agents such as I have found useful for the froth-flotation of gangue colloids as described in my aforementioned United States Patent No. 1,445,989. In general, therefore, I may say that I have found that the flotation agents which are best adapted for the flotation of sulfid minerals, and are commonly used for that purpose in the present froth-flotation art, are either useless or distinctly inferior for the flotation of barite, whilst the agents that I have found to be of .unusual effectiveness'for the flotation of barite are those which are either useless or decidedly inferior for the flotation of sulfids.

I have found, as the result of my investigations, that soaps are excellent agents for the froth-flotation of barite under roper conditions of application which will e described in detail in what follows. There is some variation in the results secured with the many different soaps which are available, but I have found generally that soaps are capable of .yielding high grade barite concentrates with a high recovery of the barite contained in the ore. As is well known to those skilled in the art of froth-flotation, soaps are generally capable of yielding copious forths when used in any of the existing types of froth-flotation machines, but because of their tendency to lift gangue and gangue colloids, thus forming dirty, overstabilized froths, they have been used to only a limited extent in the froth-flotation of sulfids.

The concentration of barite by froth-flotation in accordance with the present invention differs from the prior art froth-flotation of sulfids and other minerals of metallic, adamantine, or resinous lustre in that the invention makes application of my discovery that soaps and other agents which are generally inefficient for the froth-flotation of sulfids are excellent agents for the froth-flotation of barite and are capable therewith of yielding high grade concentrates with high recoveries of the barite contained in the ore or other barite-bearing material.

I will have frequent occasion, in this specification, to refer to laboratory tests on the flotation of barite ores and I will, therefore, describe my customary procedure for conducting such tests.

In cases where no removal of the colloidal constituents of the ore pulp is to be conducted, I wet grind a one kilogram (dry weight) sample of the ore in a laboratory ball mill until all of the material passes a screen of the desired-mesh. I then dilute the sample with water so that the pulp contains about five and one half parts of water to one of ore by weight and place this Ipulp in a laboratory flotation machine, or cc 1, of the pneumatic type.

The pulp having been placed in the rougher cell, the desired kind and quantity of flotation reagent is added and air is bubbled through the porous blanket. forming with the flotation agent, a barite-bearing froth which ispermitted to overflow gently, thus removing the flotable mineral. From time to time samples of the tailing are withdrawn from the cell for examination and returned'through the feed pipe, and the liquid coming over with the concentrate froth is separated at intervals and returned to the cell through the feed pipe, thus maintaining a practically constant dilution within the cell and returning part of the flotation agent which is used repeatedly. Further additions of fresh'. flotation agent are made if and when required and a run is considered complete when the froth no longer contains any considerable quantity of the flotable mineral and when the tailings appear to be relatively free of such mineral. At this point, the material remaining in the cell is removed and evaporated to dryness, this residue forming the tailing from the test. The concentrate is diluted, as required, and placed in the small or cleaner cell, addltional flotation agent being added if necessary. At the first pass of the cleaner a cleaner concentrate is made, the material remaining in the cell at the end of the run constituting middling which is removed and evaporated to dryness. The cleaner concentrate is replaced in the cleaner cell, diluted with appropriate deflocculating agent,

water as required, additional flotation agent added if necessary and again frothed to produce the final or re-cleaner concentrate which is evaporated to dryness, whilst the material remaining in the cell, known as the second or re-cleaner middling is added to the first or cleaner middling and evaporated to dryness.

Unless otherwise noted, all tests are run in a practically neutral pulp, and unless specifically mentioned, no other agent than the flotation agent is added. The testsare usually run at room'temperature.

When it is desired to deflocculate the colloidal constituents of the ore pulp, I add an enerally sodium silicate, either to the pulp before it is ground in the laboratory ball mill or to the pulp which is ready for flotation, just enough of the sodium silicate or other deflocculating agent bein used to secure the desired result. The then placed in the rougher cell and treated as above described.

When I desire to remove a portion of the colloid content of the'ore, I generally add the required amount of sodium silicate or other deflocculating agent to the ore in the laboratory ball millilthus grinding the ore in the resence of t e deflocculating agent.

When t e ore is ground to the desired fine-' ness, I dilute with water, forming a pulp in which the colloids are deflocculated. This pulp is allowed to stand quietly in tall cylinders for several hours or until the greater part of the non-colloidal portion of the pulp has settled out. The supernatant colloidbearing liquor is then carefully decanted. The settled material is re-pulped with an appropriate quantity of water and, if necessary, an additional amount of deflocculating agent is added. These steps are repeated until the colloid content of the pulp has been reduced to the desired extent, which is indicated by experiment, whereupon the final residue is diluted with water and placed in the flotation machine as previously described, while the colloid-bearing liquid,

which has been decanted in the several steps above mentioned, is evaporated to dryness. It will thus be seen that starting with a dry weight of one kilogram of feed sample of known composition, I recover a concentrate, a middling and a tailin product, or a colloid, a concentrate, a mi dling, and a tailing product from each test. Each of these roducts is evaporated todryness, weighec and analyzed, and from the figures so obtained, the grade and recovery are calculated.

No. 400 crude wood creosote oil, manufactured by The Pensacola Tar &'Turpentine Company, is a product of the destructive distillation of yellow pine wood and, according to .its manufacturer, it has the following characteristics: specific gravity 1.025; distillation point 190 C. to 360 C.; refractive index 1.4977 viscosity 2.9. I had noted in connection with my investigation of the recess described and claimed in my United S tates Patent 1,445,989 that this oil, especially when used in considerable amounts, had a decided tendency to form colloid-bearing froths and even to float gangue. It was, therefore, tested as a barite flotation agent and under conditions hereinbefore describe in which the colloids of the barite ore ulp have been preliminarily partly removed by defiocculation and decantation. This oil I found to be a fair flotation agent for barite. In one test the barite concentrate contained 94.88% BaSO with a recovery of 68.7% of the barite contained in the feed sample, and in another test the barite concentrate contained 98.29% BaSO with a recovery of 59.9% of the barite contained in the feed sample. It is probable that the results secured with this oil are due to its relatively hi h pitch content, because, as previously pomted out, oils having a high pitch content appear to have a tendency to lift minerals which are generallyclassified as engue.

Oleic acid, historically, is one of tlie oldest oils used in flotation, and it was used, prior to the introduction of froth-flotation in the Cattermole granulating process and in various film flotation processes. When froth-flotation was developed from these older processes, oleic acid was naturally one of the oils first employed, and for a time it was used commercially in the flotation of sulfide; but, so far as I am aware, only in acid circuits. This oil, it is believed, is no longer used for the froth-flotation of sulfids. because of its notorious gangue-lifting character. To determine the suitability of oleic acid as a barite-selective flotation agent, I performed a test in which one kilogram of ore, after removal of a part of the colloid content, was floated in the presence of one cubic centimeter of oleic acid, and I secured a concentrate containing 99.53% B2130 with a recovery of 64.7% of the barite contained in the original feed sample. It will be seen that under the special conditions of preparation of this sample, by which the gangue colloids had been preliminarily removed, the oleic acid gave a high grade concentrate and a fair recovery, but it is probable that with out preliminar colloid removal this oil would be capabl e of yielding only low grade barite concentrates. The sample of oleic acid. used in the test above referred to, was obtained from the Proctor & Gamble (10., Cincinnati, Ohio, and was evidently of commercial grade.

\Vinter pressed menhaden fish oil gave the same general results as olcic acid. It was not as good a frothing agent, but it lifted barite strongly and yielded a concentrate containing 97.66% barium sulfate with a recovery of 62.9%. Here also the test was made on a pulp from which the gangue colloids had been in part removed by deflocculation and decantation, and it is probable that had the oil been used without this preliminary treatment of the pulp that a low grade barite concentrate would have resulted. Fish oils have been used to a slight extent in times past for froth-flotation of sulfids, but, I believe. have been entirely abandoned for that purpose because of their relatively poor selection as between sulfids and gangue. It is probable that this action is due to the relatively high content of olcic acid, and closely related fatty acids, contained in fish oils.

Cottonseed oil pitch is a by-product of the refining of cottonseed oil, and, so far as I am aware, has never before been used as a froth-flotation agent. I have made tests with three samples of this substance, manufactured by the N. K. Fairbanks (10., and known respectively as soft. medium and hard pitch, the first being a liquid, the second a stiff paste and the third a solid tarlike substance. The soft pitch was slightly miscible in water when heated and stirred into the pulp. It gave very little froth in the flotation cell and could not conveniently be used in that form. The medium pitch and hard pitch were almost entirely immiscible in water. even when heated. Vhen these substances were dissolved in gasoline, they gave excellent results in barite flotation. The gasoline possesses some frothing power, but by itself did not yield a satisfactory grade or recovery of barite. The cottonseed oil pitches, when dissolved in gasoline, yielded copious froths and evidently had a. high degree of selective power for barite. In a test run with cottonseed oil hard pitch dissolved in gasoline, on a pulp from which the colloids had been in part removed by deflocculation and decantation, a barite concentrate containing 98.28% BaSO, was obtained with a recovery of 80.5% of the barite contained in the original feed sample and a loss in the tailing of only 5.2% of the original barite. It will later be seen that cottonseed oil pitch dissolved in gasoline gives with barite results very similar to those secured with soap.

Depending upon the temperature and the relative amount of water, soaps may exist in water in two forms of solution; true or molecular solution, and colloidal solution. There are a number of important differences in the behavior of a given soap, depending upon whether it is in true solution, in colloidal solution, or exists partly in each state. It is possible not only to have solutions of soap in water, but also of water in hydrated soap, but into these complications it is not here necessary to enter. A full discussion of the properties of soap-water systems may be found in Soaps and proteins by Martin H. Fischer, New York, John Wiley & Sons, Inc, 1921. In general, it may be said that at a given temperature potassium base soaps of a given fatty acid pass into solution more readily than the corresponding sodium soaps, and also that, considering three members of the acetic acid series of fatty acids, the soaps of lauric acid pass into solution more readily at a given temperature than the corresponding soaps of palmitic acid, and these, in turn, are more readily soluble than the corresponding soaps of stearic acid, which is a still higher member of this series of fatty acids.

There are a number of series or groups of fatty acids, into the details of the behavior of which in soaps it will not be herein necessary to enter. It is sufiicient to say that, in general, the higher members of these series form, with a given base, soaps which are less readily soluble in water than are soaps of lower members of the same series. This difference in the behavior of soaps gives rise to the distinction between cold water soaps and hot water soaps, and between hard water soaps and soft water soaps. Soaps containing considerable quantities of lauric acid and other fatty acids occupying about the same relative place in their respective series are quite readily soluble in cold water and are not readily precipitated or salted out by electrolytes. Therefore, such soaps may be used in cold water or in salt water, and it is for this reason that cold water soaps andsaltwater soaps are made from such oils as cocoanut oil which contain a large percentage of lauric and closely related fatty acids.

Soaps composed principally of palmitic and closely related acids go into solution at medium temperatures and these are generally made from cottonseed oil and similar oils containing considerable quantities of.

water.. Most commercial soaps consist of a mixture of soaps of several fatty acids, sometimes with more than one base, in order to give thema wide working range of water temperature. But for special purposes, soaps can be, and often are, made by a suitable selection of base and fatty acids, so thatthey will have a limited working range as to the temperature of the water in which they are used, but will be more efl'ectiv'e within that range than the mixed soaps.

I believe it is likely that the soap or soaps used, to be effective as barite flotation agents, should be in colloidal solution in the ore pulp rather than in true solution, and assuming this to be the case, it will be clear from the above discussion, that: the choice of soap, both as a) base and as to fatty acid, depends somewhat upon the temperature of the flotation pulp. Thus, in very cold pulp, soaps like cocoanut oil soap, containing a considerable percentage of lauric acid and especially potassium base soaps of such fatty acids and soaps made from rosin, and containing a considerable ercentage of abietic acid, will probably give the best results. They will be sufhciently soluble to go into colloidal solution in the cold pulp, but not so soluble as to go entirely into true solution. For pulps of medium. temperature, soaps containing considerable percentages of palmitic and oleic acids will best'serve the purpose, whilst for hot pulps, soaps containing a large percentage of stearic and related fatty acids will probably be best.

It is probably for reasons such as those just stated that certain soaps give "better results than others when used in barite ore pulps at normal temperatures; that is, in pulps wherein the water has been used at the temperature at which it is delivered to the plant, which will, of course, vary somewhat, depending upon the season and similar cir cumstances. Thus, working between temperatures of 45 F. and F., I have generally found that the sodium base soaps (which are cheaper than potassium base soaps) of a given fatty acid give slightly better results than the corresponding potassium. base soaps, probably because at such temperatures they are sufioiently soluble to form colloidal solutions in the pulp but not so solub e as to form true solutions at the temperature and with the quantity of water which is available. For perhaps the same reason, the soaps containing considerable quantities of abietic, lauric, .palmitic and oleic acid seem to work best at ordinary temperatures.

. It seems probable, also, that various soaps display, for the flotation of barite, the same sort of effects which various oils display when used in the froth-flotation of sulfids. As is well known to those skilled in the art, some sulfid flotation agents are excellent frothing agents, but are deficient in gathering or collecting value, and it is, therefore, common practice to use several oils for the flotation of a given sulfid. A frothing oil, to produce the froth, and a gathering oil to coat the sulfids or to stabilize the froth.

Similarly, when using soaps for the frothcopious froth, and with it, a certain amount of a hard soap, containing a considerable amount of stearic acid, such as a soap produced from beef tallow. Such a soap, while insufficiently soluble at the temperature of the pulp to yield a copious froth, seems to be of value as a barite gathering or frothstabilizing agent.

When it is desired to use for barite flotation a fat, grease, tar or a soap composed of a fatty acid or abase, or both, which renders it insufficiently soluble in water of the given temperature to effect the desired result, it may be dissolved in gasoline, ether, turpentine, carbon disulfid, carbon tetrachlorid, alcohol, or some similar solvent, and then introduced into the flotation pulp. The common mechanical lubricating greases consist of mixtures of stearic, oleic and other acids combined with calcium, magnesium and aluminum as the bases. These may be out with a solvent, and used for barite flotation, as described for other soaps.

Thus, using 2- grams ofNo. 1 Arctic cup grease, manufactured by The Standard Oil Company, dissolved in 50 cubic centimeters of gasoline, I made a test on a sample of Cartersville jig tailings containing 56.5% BaSQ from which, after part of the col- "loidal constituents had been removed by deflocculation and decant'ation, I secured by flotation a concentrate containing 98.3% BaSO with a recovery of 75.4% of the barite contained in the original sample.

Similarly, using tailings containing 55.34%

BaSO and 2 grams of Mercks Lanolin anhydrous, Lanum (wool fat), I secured a concentrate containing 98.44% BaSO, with a recovery of62.9%.

In arriving at the principles of the present invention, I have made a long series of comparative tests, using the same ore ground to the same mesh in each case, and varying only -in the kind of soap used to float the barite. Many kinds of commercial soap and several typical specimens of pure saponified fatty acids have been used. In all cases the pulp was partly freed of gangue colloids by deflocculation and depantation. All these soaps gave excellent results both as to grade of barite concentrate and recovery of barite but as there was some difference in their behavior, I have divided them into three classes as follows: Class A:-Soaps possessed of great frothmg power but not necessarily very highly selective for barite; Class B :-Soaps having lower frothing power than the Class A soaps but which are highly selective for barite; Class C:Soaps of lower frothing power than ClassB soaps and, therefore, requiring more soap for the flotation of a given quantity of barite, but possessed of high selective power for barite. It will be understood that this classification is only approximate and may vary somewhat, depending upon the barite ore which is used in makin the tests, upon the degree of dilution 0 the pulp, the amount of gangue colloid present, the pulp temperature, and other such factors. To secure the best results with a given sample of ore, I find that it is often desirable to use a mixture of a Class A soap with a Class B soap, or of a Class A soap with a Class C soap. It is to be understood that this classification is based only upon the frothing power and barite selectivity of the soaps and does not imply that a Class A soap necessarily gives higher grade concentrates and better recoveries than a Class B soap, or that a Class B soap is superior in such respects to a Class C soap. Generally, to secure a given result as to grade and recovery, more Class B soap is required than of a Class A soap, and more Class C soap than of Class B, and the choice in practice would depend upon considerations of cost and convenience as well as upon the results which it is desired to secure.

As the result of my investigations, I include in ClassA:

Name oi soap Name of manuiacturer Fels & 00., Phila, Pa. The FBlIl J EDkS 03., N. Y.

Louisville Food Products 00., Louisville, Ky. Fairbanks 00., N

Lenox- Labor Saver Soap Fairy Soap Y. Vegetable Wonder Wag's Soap 00., Knoxville, Tenn. Rosin Soa Applicant.

D Sodium Soap-Cottonse H. A. Gardner, Laboratory, Washu iHgtOn, 2 0' Potassium Soap Sodium Soap-Cocopnut Q iL .Ivory Son Class 13- Name 0! soap Name oi manufacturer Servus Wiiite Napiitb Servus Borax Servus White Flo. Export Borax. Grandma's Whitc Joy White Naphtba u u u Globe Soap 00., Cincinnati, Ohio.

Louisville Food Products 00., Louisville, Ky.

Santa Claus Fairbanks 00., New York.

Palm Royal. liasirius Bros, Sioux City, lowa. Palmolive.-." Paiinoiivesonp 00., Milwaukee, Wis. Uncle Sam 'lar-. Andrew Jergens Co., Cincinnati, 0.

Davies Young Soap 00., Dayton, 0. H. A. Gardner, Laboratory, Washington, D. 0.

u n n Buckcye Cleanser Potassium Oleate...

Sodium Oieate Sodium Soap-Winter Pressed Menbaden Oil.

Potassium Soap Winter Pressed Menhadcn Oil.

Sodium Soap oi rosin acids u u u Potassium u u i. Sodium Soap oi soya bean oil. Potassium u .i i. r, u Sodium soap oi linseed oil-.

Glass (7- Name oi soap Name of manufacturer Oval Pearl Soap "l Globe Soap 00., Cincinnati, 0. Peek-A-Boo .1 Hpsklns Bros. 6: 00., Sioux City, i own. White Nnphtha Proctor dz Gamble, Cincinnati, 0. Clean-Easy Louisville Soap 00., Louisville, Kentacky.

Cudahy Soap Works, 50. Omaha,

Nebraska.

Colgate 6t 00., N. Y.

Cudahy's Soap Octagon White Floating.--

Sodium Stearato Eimer 6:. Amend, N. Y. Sodium Oieate-..

La Calana Castile Swiit 6c 00., Chicago, ii]. [001 p n u u Al u u Corn Oil Soap Corn Products Refining 00., N. Y. Soghum soap oi China Wood HbAbGarduer, Laboratory, Wash.

u on u' u u n Potassium I have hereinbeiore referred frequently to the removal from the barytesore pulp of colloidal constituents by a process involving deflocculation or dispersion of such colloidal constituents, and their removal in part from the pulp by decantation. It is well known that certain colloidal constituents of ore pulps are prejudicial or inhibitory to the flotation of sultids and I have found, likewise, that when barite ores are ground to a size which renders them convenient for treatment by froth-flotation, there generally exists in the pulp colloidal matter which is prejudicial to securing the maximum grade of barite concentrate, the maximum recovery of barite, or both, by froth-flotation.

A large proportion of the barite ore at present mined in the United States is derived from so-called residual deposits, and since the gangue in which the barite nodules of such ores occur is principally clay and earth, it will be understood that barite oresiii) colloidal washer tailing is, therefore, associated with an extremely large amount of colloidal matter. The jig tailing and other waste baritebearing products of present methods of treatment also contain considerable quantities of colloidal matter, and even the barite concentrate derived from ores such as those described by existing methods is stained and contaminated by colloidal substances.

Barite ores derived from vein or bedded deposits do not generally contain as much matter as those derived from residual deposits, but in the fine grind.- ing of barite ores to the degree required to produce suitable conditions for froth-flotation of the barite, there is almost invariably produced or released a sufficient amount of colloidal material to exercise a deleterious effect upon the froth-flotation treatment of the barite.

Since the agents which have a marked selective action for barite and tend to float barite are also in general those which, as described in my aforementioned United States Patent No. 1,445,989, tend to form colloid-bearing froths, it will be understood that in connection with barite ores, in order to secure the particularly high grade concentrates which are called for by the bariteconsuming trade, the preliminary removal of colloids, as 'contemplatedby my United States Patents No. 1,448,515, dated March 13, 1923, and No. 1,454,838, dated May 8, 1923, is of particular value and importance.

In some cases, as where the ore contains a relatively small amount of colloids, it may be sufficient, in order to secure good results, to bring about the deflocculation or dispersion of such colloids preliminarily to flotation, but ordinarily, better results can be secured in all cases by deflocculating and then decanting at least a part of the colloidal constituents associated with the barite ore pulp before the ore is subjected to frothflotation treatment.

Since barite is a relatively soft and brittle mineral, I find that in barite-bearing log washer tailing, and similar products, and in barite ore pulps which have been ground to a degree suitable to prepare them for flotation, that often considerable of the barite itself becomes colloidal within the meaning which I have assigned to that term in my aforementioned United States patents, to wit, The colloidal matters may be present as pure colloids, organic or inorganic, or in a state bordering on the socalled coarse suspensions.

Throughout this specification and the appended claims, I intend to embracein the expressions colloids, colloidal slimes, and colloidal constituents, both true colloids, and those quasi or borderland substances which may not be truly colloidal but partake of the qualities .of, or resemble,

colloids, and without regard to the sources from which such colloidal matters are derived. Thus, for the purposes of the present invention, the colloidal constituents may be considered as ranging from just above and are capable of existing in both the sol or gel state, or of being dispersed and coagulated or flocculated and deflocculated. By a colloidal slime, therefore, I mean a material which is not necessarily a true colloid, but which exhibits colloidal charaoteristics to a sufficient degree to make it amenable to the manipulation herein described.

Some of the barite itself generally exists in a colloidal condition in the flotation pulp, and I have found that even when the pulp contains a minimum of other colloidal constituents that it is generally desirable to preliminarily remove colloidal constituents, including colloidal barite, before subjecting the barite-bearing ore pulpto froth-flotation treatment, forthe reason that colloidal barite floats with extreme ease and it, therefore, tends to unduly armor or coat the bubbles of the froth, producing a condition generally known as ovenstabilization. This condition of over-stabilization, regardless of whether it is brought about by barite or by other colloidal constituents, is an objectionable condition because it tends to mechanically entangle or entrain gangue particles, and to carry them over into the concentrate.

It Will be clear from this discussion that in the flotation of barite, colloidal constituents may in several different Ways exert a deleterious or undesirable effect. Gangue colloids tend to pass into the froth, thus contaminating the concentrate directly, by reducing its grade, and indirectly by creating over-stabilization of the froth and thus further reducing the'concentrate grade by carrying over gangue particles. Such colloids also often exert a direct inhibitory action on the flotation of the coarser particles of barite, causing them to tend to remain in the tailing, thus reducing the recovery of barite. Colloidal barite, while perhaps not in anyway interfering with the recovery, does tend, by over-stabilization of the froth, to carry over gangue particles which should remain in the tailing.

The process of deflocculation anelclecantation, by which the colloidal constituents are in part separated from the ore pulp, depends upon the fact that by dispersing and deflocculating .such colloidal constituents they can be held in suspension in quiet pulp. That is, that they can be given a practically zero settling rate, whilst the non-colloidal constituents of the pulp are permitted to settle. In the practice of the process, when sedimentation of the non-colloidal particles has progressed sufficiently, the bulk of the liquid, containing the suspended colloidal constituents and small amounts of extremely fine slow settling non-colloidal constituents, is decanted from the sediment, as described in detail in my United States patents to which reference has been made.

In the case of barite ores, the colloid suspension is often of such character and quantity as to justify the recovery of its solids as a by-product. This material contains solids in such an extremely fine state of division that when dried and appropriately prepared for the market it is salable. as a mineral filler, scouring powder or as offcolor barytes. The colloidal and other solids contained in such a decanted suspension may thus be separated and recovered from the water in which they are suspended by flocculating them with appropriate agents and permitting them to settle in the form of a mud or sludge. Or they may be flocculated and se arated from the bulk-of the water with wiich they are associated by a frothflotation treatment, according to the process described in my United States Patent 1,445,989. The solids may be recovered from the aforementioned sludge, or from the colloid-bearing froth just referred to, by vacuum filtration, or by evaporation of the water, or by a combination of these two means.

The process of the present invention may be carried out in standard froth fiotation machines, either of the so-calledagitation type, or of the so-called pneumatic type, or in the machines which represent a combination of the principles of the two preceding types. I prefer to use the pneumatic type machines because of the great capacity which; it is possible to secure from a. given size machine, and the greater ease of regulation and control. But, as usual in the treatment of minerals by flotation, certain circumstances connected with the ore, the location of the mill, the cost of power and of skilled attendance often indicate some one type of flotation apparatus as being better suited to the situation than others.

I have found that the degree of comminution to which the barite ore must be subjected to fit it for froth-flotation recovery of its barite content does not differ reatly from that to which sulfid ores inten ed for flotation are ordinarily reduced. In an event, the ore must be ground fine enoug to secure effective severance of the diverse minerals which it contains, and, in general, it is not practicable to float material coarser than that which will pass 35 mesh Tyler standard sieve. Working with a sample of barite-bearin jig tailing from a barite concentrating p ant located at Cartersville,

Georgia, with which all the conditions of ex eriment were kept as nearly as pract1- ca le identical, except that the degree of comminution of the ore was varied, I found that the degree of comminution in this case, where the minerals are ractically free from attachment to one anot ier at 35 mesh, had practically no bearing upon the results which could be secured.

I have found that in barite flotation, the considerations respecting dilution of the pulp are the same as they are in the flotation of sulfids. The degree of dilution will depend upon the character of the ore, the fineness of grinding, and similar considerations. Only rarely is the dilution greater than six weights of water per weight of ore, or less than three weights of water per weight of ore. Dense pulp generally gives greater capacity to the flotation machines, but might make it more difficult to secure high grade concentrate and usually a smaller quantity of flotation agent suffices with a. dense than with a more dilute pulp.

The effect on the flotation results of floating the barite respectively, (a) in the presence of the naturally flocculated colloids of the ore pulp, (b) in the presence of the colloids of the ore pulp after they have been deflocculated, and (c) in an ore pulp from which the colloids have been in part removed by preliminary deflocculation and de- 'cantation, is illustrated in the following examples. In each case, the procedure, previously described, was followed and the same kind and amount of flotation agent (rosin soap) was employed at the rate of 1.2 pounds per ton of feed, each sample being ground to pass 80 mesh. A sample of Cartersville jig tailing, containing 61.81% ba- 3 rium sulfate was used in these examples.

Example].

Cone. grade Recovery 90. BuSOi 45. 0% 08. a [141.80% 98.82% 71.5%

A similar series of tests, made upon a i Example II.

Cone. grade Recovery Another series of tests, run on an ore containing an intimate mixture of silica, barite and fluorspar (55.8% 132130,, 4.7% F as CaF from a mine at Sandy Bottom, North Carolina, using rosin soap at the rate of 0.60 pound per ton of feed as the flotation agent, gave results as follows:

Example III.

Per cent Conc. grade Recovery F as can (a) 83.30% B8504 40.1% 3. 90 (b) 90. 0 49.2% 1.40 (c) 90. 56. 0% 1. 60

Another series of tests, run on Cartersville mud (log washer tailings), containing 1.11% BaSO using rosin soap, gave results as follows:

Example I V Conc. grade Recovery g t g (a) .75%B&SO4 2.70% 1.65 (b) 7. 3. 20% 1. 51 (c) 71.63% 63. 20% 1. 40

pulp. When, because of other circumstances,

such as the natural acidity of the mine water, it is desirable to conduct the flotation on an acid pulp, certain modifications may be necessary if it should be impracticable to neutralize the acidity of the pulp, as by the use of lime. Thus, a soap may be used which is not readily salted out, as, for example, a cocoanut oil soap, or other salt water soap, or a reagent may be used which will work in acid pulp.

As is commonly the practice in the flotation of sulfids, it may, in the case of certain barite ores, be necessary to employ certain addition agents for the purpose of properly conditionin the pulp. Thus, it may be necessary to a d lime, or some other alkali, to overcome acidity, or sodium silicate, gumarabic, trisodium phosphate, or some similar agent, to secure or maintain defiocculation, as hereinbefore described, the need for such addition agents and their selectlon necessarily being determined by comparative tests, as will be understood by those skilled in the art to which this invention relates.

The temperature of the barite-bearing flotationpulp may, if necessary, be varied as by cooling the pulp-by dilution with cold water or by passing it over cooling towers, or by heating it, as by the introduction of steam; but on the score of cost, it is genera d i a to ndu t fl at on at th e ural temperature of the mill water, and, generally, other factors affecting the flotation can be controlled so as to permit of this. In the practice of the process of the invention, keeping in mind the necessity for producing very high gradeconcentrate with a maximum recovery at the lowest possible cost for investment and operation, tests should be made on each ore which it is desired to treat, in order to determine the optimum conditions relating to degree of grinding of theore, deflocculation, or removal of colloids, neutrality, alkalinity or acidity of the pulp, the degree of dilution of the pulp, and itstemperature, the agent or agents to be used for conditioning the pulp and securing the barite flotation, and the type of flotation machine.

From many similar tests, the following examples are selected as representative of the results which may be obtained with several ores, by practise of the preferred form of the process of the present invention. The feed sample, consisting of 1 kilogram of Cartersville jig tailing containing 66.5% barium sulfate, was ground to pass 80 mesh, and treated by deflocculation and decantation for removal of part of the colloidal constituents.

Example V.U'sing one gram of Ivory soap manufactured by Proctor and Gamble (10., or at the rate of 2.00 pounds of Ivory soap per ton of material treated, the following results were obtained:

Per cent Per cent Per cent Gms. ample Grams of mm orBaso. Baso. mm BaSO4 Analysis of feed sample 66.5% BaSO Analysis of material lost, assumed same as feed. TCalcnlated analysis of feed sample.

Example VI.In another test using- 1.2 grams of Mascot soap, manufactured by the Fairbanks Co., or at the rate of 2.4 pounds of soap per ton of material treated, the following results were obtained:

' Per cent Per cent Per cent Gms. Sample Grams of total olBeS04 Baso. B8804 Analysis or feed sample 66.5% 32180;. 1' Calculated analysis of teed sample.

Example VIl.-In another test, I used 25 c, c, of a solution of N. K. Fairbanks 00.,

cottonseed oil hard pitch, 10 grams dissolved in 100 c. c. of motor gasoline, or at the rate of 5 pounds of hard pitch and 6 gallons of asoline, per ton of material treated. The feed sample was one kilogram of Cartersville jig tailings containing 62.5% B2150 1 Calculated analysis of feed sample. Actual analysis of feed sample.

Ewample VIIIJ In another test I used one kilogram of ore from the Lawton mine in North Carolina. This ore consisted of an intimate mixture of barite and quartzand contained 88.33% B1180 It was ground to pass 80 mesh Tyler standard, and defiocculated by the addition of 2 c. c. of 40 B. commercial sodium silicate to the pulp in the grinding mill. The colloids were thereby defiocculated, but as the amount of colloidal suspension was not too great it was not decanted. Rosin soap at the rate of 1.2 pounds and Proctor and Gamble (30., White floating naphtha soap at the rate of 0.4 pound per ton of material treated were used, with the following results:

Per cent Per cent Per cent Gms.

Sump Grams of total 61 nusol 1311801 ;;33"

pass mesh, using about 300 c. c. water and 3 c. c. of 40 B. commercial sodium silicate. It was thus deflocculated and after a suitable settling eriod the coloidal suspension was decanted and the sediment diluted and treated by flotation, using rosin soap at the rate of 0.6 pound per ton of original ore. The results were as follows:

' Calculated feed analysis.

tActual feed analysls.

The mineralogical composition of the concentrate was 95.0% BaSO 2.05% CaF and 2.95% SiO which represents material that can satisfactorily be used for lithopone manufacture.

By means of the process of the present invention, it is possible to produce very high grade barite concentrates with a high ercentage recovery of the barite containe in the ore, thus making it possible to improve the grade of barite ores which are now n'larketable, but whose value can be enhanced by further improving their grade. Ores not heretofore amenable to commercial exploitation can be.economically treated for the recovery oil their barite content. Waste rodnets of present methods of barite ore ress' ing can be reclaimed and retreated. Manufacturing processes, in which barite is used,

can be simplified and cheapened by the this final concentrate is the product of one or more froth-flotation operations. In other words, where the froth-flotation treatment involves rougher, cleaner and perhaps recleaner operations, the ultimate recovery is based on the barite content of the final cleaner (or recleaner) concentrate and the barite content of the original feed to the first or rougher froth-flotation operation.

I claim:

1. The method of concentrating baritebearing material by froth-flotation which comprises subjecting the barite-bearing material to froth-flotation in the presence of a barite-selective flotation agent containing soap and thereby elt'ecting a substantial recovery of the barite in the resulting concentrate.

2. The method of concentrating baritebearing material by froth-flotation which comprises subjecting the barite-bearing material ground in a pulp to flotation size to froth-flotation in the presence of soap and terial to froth-flotation in the presence of ill soap and thereby efiecting a substantial recovery of the barite in the resulting concentrate.

4.. The method of concentrating baritobearing. material, by frothflotation, which comprises grinding the barite-bearing material to flotation size in the presence of sodium silicate, subjecting the resulting pulp to sedimentation and decantation in the course of which there is decanted a substantial amount of colloidal constituents in a dispersed condition, and subjecting the remaining pulp to froth-flotation in the pres- I ence of soap and thereby efl'ecting a substantial recovery of the barite in the resulting concentrate.

5. The method of concentrating by frothflotation barite-bearing material associated with colloidal matter in a pulp which comprises removing colloidal matter from the pulp, said removal of colloidal matter being preceded by the step of dispersing or de flocculating colloidal matter which would otherwise be present in the pulp in a flocculated condition, and thereafter subjecting the remaining pulp to froth-flotation in the presence of a barite -selective flotation agent.

6. The method of concentrating by froth flotation barite-bearing material associated with colloidal matter in a pulp which com prises removing colloidal matter from the pulp by decantation in the course of which a portion of the water forming the pulp is also removed, said removal of colloidal matter being preceded by the step of dispersing or deflocculating colloidal matter which would otherwise be present inthe pulp in a flocculated condition, and thereafter subjecting the remaining pulp to froth-flotation in the presence of a barite-selective flotation agent. i

7. The method of concentrating by frothflotation barite-beming material associated with colloidal matter in a pulp which comprises dispersing or defiocculating colloidal matter which would otherwise be present in the pulp in a flocculated condition, and thereafter subjecting the pulp to froth-flotation in the presence of a barite-selective flotation agent.

8. The method of concentrating by frothflotation baritabearing material associated with colloidal matter in a pulp which comprises addmg to the pulp a dispersing or deflocculating agent and thereby dispersing or deflocculating colloidal matter which would otherwise be present in the pulp. in a fiocculated condition, and thereafter subjecting the pulp to froth-flotation in the presence of a barite-selective flotation agent.

9. The method of concentrating by frothflotation barite-bcaring material associated with colloidal matter in a pulp which comprises removing colloidal matter from the pulp, said removal of colloidal matter be ing preceded by the step of dispersing or deflocculating colloidal matter which would otherwise be present in the pulp in a flocculated condition, and thereafter subjecting the remaining pulp to froth-flotation in the presence of soap.

10. The method of concentrating baritebearing material by froth-flotation which comprises grinding the barite-bearing material to flotation size in the presence of water and a colloid dispersing or deflocculating agent and thereby producing a pulp containing dispersed or deflocculated colloidal matter, treating said pulp to remove therefromto a desired extent said dispersed or deflocculated colloidal matter, and thereafter subjecting the remaining pulp to frothflotation in the presence of a barite-selective flotation agent.

11. The method of concentrating baritebearing material by froth-flotation which comprises subjecting the barite-bearing material to froth-flotation in the presence of a soap capable in the froth-flotation operation of effecting an ultimate recovery of at least of the barite in a concentrate containing not less than 90% barite.

12. The method of concentrating baritebearing material by frotl1-flotation which comprises subjecting the barite-bearing material to froth-flotation in the presence of a barite-selective soap and thereby effecting a substantial recovery of the barite in the resulting concentrate.

13. The method of concentrating by frothflotation barite-bearing material associated with colloidal matter in a pulp, which comprises removing a part of the colloidal matter from the pulp, and thereafter subjecting the remaining pulp to froth-flotation in the presence of a barite-selective soap.

14. The method of concentrating baritobearing. material by froth-flotation which comprises subjecting the barite-bearing material to froth-flotation in the presence of soap and thereby effecting an ultimate recovery of at least 60% of the barite in a concentrate containing not less than about 98% barite.

15. The method of concentrating baritebearing material by froth-flotation which comprises grinding the barite-bearing material to flotation sizedn the presence of water and sodium silicate an dthereby pro- Hit) ducing a pulp containing dispersed or deflocculated colloidal matter, subjecting said pulp to sedimentation and dccantation in the course of which there is decanted a substantial amount of said dispersed or dcflocculated colloidal matter, and thereafter subjecting the remaining, pulp to froth-flotation in the presence of soap and producing a concentrate containing about 98% barite and 10 an ultimate recovery of at least 60% of the barite.

16. The method of concentrating by frothflotation baritc-bearing material associated with colloidal matter in a pulp, which comprises removing a part of the colloidal matt er from the pulp, and thereafter subjecting the remaining pulp to froth-flotation in the presence of a barite-sclective flotation agent.

In testimony whereof I affix my signature.

WALTER O. BORCHERDT. 

